Prior art force transducers, particularly load cells, range widely in their basic design depending upon such factors as the mechanical placement of the load cell in the subject application, the sensitivity required, and the environment in which the load cell is used. In continuous casting operations where a mold is used to form a cast product, the mold walls are typically moved relative to other mold walls through use of a clamping bolt driven by screw jacks to form products of various dimensions. The force supplied by the clamping bolt has been found to be a critical parameter in these operations. Thus, load cells are frequently used to detect and control the force exerted by the clamping bolt during casting operations.
A typical load cell application involves passing the clamping bolt through the load cell wherein the load cell is intermediate the force application means--the clamping bolt--and the object desired to be moved--the mold wall; thus, a through hole load cell is required. The prior art through hole load cells used in continuous casting applications are of the tubular or column element type where the force applied by the clamping bolt is transferred axially through the column to the mold wall, thus placing the column in compression and creating a strain that is sensed by a plurality of biaxial strain gauges mounted around the surface of the column. This design has proven unsatisfactory because accurate force measurements for column type load cells depend on a true parallel application of the force to the column element. If the force or load applied to the column is not on-axis, the column will be subjected to a bending load; i.e., the component of the applied force that is off-axis. This bending load creates a strain that will be detected by one of the biaxial strain gauges and will introduce an error in the load cell force measurement output. Moreover, prior art load cell systems have proven unsatisfactory in the continuous casting environment because of temperature nonlinearity in the load cell output caused by the wide temperature changes associated with the casting process. Further, the casting environment is extremely corrosive, thus causing an unacceptably high failure rate among prior art load cells due to inappropriate materials selection and inadequate sealing subsystem design.
Thus, there is a need for an improved load cell for generating a signal indicative of the force transmitted through the load cell that overcomes or minimizes the above-mentioned problems.